US10380397B2 - Half-bridge fingeprint sensing method - Google Patents
Half-bridge fingeprint sensing method Download PDFInfo
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- US10380397B2 US10380397B2 US14/978,442 US201514978442A US10380397B2 US 10380397 B2 US10380397 B2 US 10380397B2 US 201514978442 A US201514978442 A US 201514978442A US 10380397 B2 US10380397 B2 US 10380397B2
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
- G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
- G06V40/10—Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands
- G06V40/12—Fingerprints or palmprints
- G06V40/13—Sensors therefor
- G06V40/1306—Sensors therefor non-optical, e.g. ultrasonic or capacitive sensing
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- the present disclosure relates generally to fingerprint sensing, and more particularly to the construction and use of a fingerprint sensing array.
- User devices store various types of information and allow access to additional information through their connection to the internet and databases stored thereon. Gaining unauthorized access to a user's device may provide access to confidential information about that user that could be used to do harm, steal identity, or commit other types of fraud.
- Biometric authentication is one method by which the owner of a device may ensure that their information remains private when necessary and that access to information and systems remains proprietary.
- the differential capacitance measurement circuit may comprise a half-bridge circuit.
- the half-bridge circuit may include a first mutual capacitor formed between a row electrode and a column electrode of a array and a second mutual capacitor that is buried, or not alterable by a user.
- the first mutual capacitor may be driven with a first signal and the second mutual capacitor may be driven with a signal that is complementary to the first signal.
- the capacitance values of the first mutual capacitor and the second mutual capacitor may be substantially equal such that the half-bridge circuit is balanced, or matched at a shared node between the first and second mutual capacitors.
- the shared node between the first and second mutual capacitances may be coupled to a differential amplifier at a first input.
- a listener electrode may be coupled to a the differential amplifier at a second input. In one embodiment, the listener electrodes may be configured to provide enable mode noise rejection with the differential input stage of the differential amplifier.
- a method for providing a digital representation of a capacitance between a row electrode and a column electrode may include receiving a first signal on a node coupled to a first input of an amplifier and a second signal on a the node coupled to the first input of the amplifier.
- the first signal may be derived from a first transmit (TX) signal and a capacitance between a row electrode and a column electrode.
- the second signal may be derived from a second TX signal that is complementary to the first signal and a capacitance between two buried electrodes. Buried electrodes may be disposed such that a mutual capacitance between them cannot be altered by the presence of a conductive object on the row and column electrode.
- the method may include receiving a third signal on a listener electrode coupled to a second input of the amplifier.
- the method may also include converting an output of the amplifier to a digital value representative of the capacitance between the row electrode and the column electrode.
- a fingerprint detection array includes a plurality of transmit (TX) electrodes disposed along a first axis and a plurality of receive (RX) electrodes disposed along a second axis.
- the fingerprint detection array may include at least one RX electrode that is split into two portions that are galvanically isolated from each other.
- the portions of the split RX electrodes may be configured to function as a listener electrode, alone or in combination with other portions of other portions of split RX electrodes.
- the listener electrode comprised of the one or more portions of split RX electrodes may be coupled to an input of a differential low noise amplifier (LNA). Another input of the differential LNA may be coupled to a receive electrode.
- LNA differential low noise amplifier
- Another input of the differential LNA may be coupled to a receive electrode.
- a common mode noise detected on the one or more portions of split RX electrodes may be rejected through the differential input stage of the differential LNA.
- FIG. 1 illustrates a system including a fingerprint detection circuit, according to one embodiment.
- FIG. 2 illustrates a half-bridge differential capacitance measurement circuit, according to one embodiment.
- FIG. 3 illustrates a half-bridge differential capacitance measurement circuit with multiple buried drive electrodes, according to one embodiment.
- FIG. 4 illustrates a capacitance measurement system including a half-bridge differential capacitance measurement system, according to one embodiment.
- FIG. 5 illustrates one embodiment of an array of electrodes for use with a capacitance measurement system.
- FIG. 6A illustrates one embodiment of a top-layer of a fingerprint detection interface with a listener electrode.
- FIG. 6B illustrates one embodiment of a top-layer of a fingerprint detection interface with a listener electrode.
- FIG. 7A illustrates one embodiment of an array of electrodes with a split receive electrode.
- FIG. 7B illustrates one embodiment of an array of electrodes with split drive electrodes.
- FIG. 1 illustrates a system 100 with a fingerprint measurement circuit 101 .
- Fingerprint measurement circuit 101 may include a number of electrodes arranged in an array 102 of row electrodes 104 and column electrodes 106 , each coupled to a fingerprint (FP) controller 105 .
- FIG. 1 illustrates eight row electrodes 104 and eight column electrodes 106 , but there may be considerably more electrodes disposed along both axes. Depending on the size of the array, there may be dozens or hundreds of electrodes for each axis (row and column).
- the pitch of row electrodes 104 and column electrodes 106 may be small enough such that multiple rows or columns may be disposed within a space between ridges of a fingerprint or along a ridge of the fingerprint when a finger is in contact with array 102 .
- the exact size and pitch of the electrodes may depend on the system design requirements.
- Row electrodes 104 and column electrodes 106 may be disposed such that a mutual capacitance, C MX , is formed between them. A value of C MX may then correspond to each intersection (of row electrodes 104 and column electrodes 106 ) of array 102 . In the example of FIG. 1 , a total of 64 intersections are illustrated. Consequently, there are 64 mutual capacitances. In an array with 75 row electrodes and 125 column electrodes, there may be 9,375 intersections, and therefore 9,375 mutual capacitances. In this embodiment, there would be 9,375 mutual capacitances that may be measured and used in fingerprint imaging. Electrodes (columns and rows) with dashed lines indicate that considerably more columns or rows may be disposed along either axis.
- C MX may be used by FP controller 105 or a host 112 to construct a fingerprint image for enrollment or validation, which may be used to unlock secure functions of system 100 .
- Fingerprint measurement circuit 101 may also include a listener electrode 110 coupled to FP controller 105 and configured to provide common mode noise for rejection for measurement of C MX .
- Common mode noise may be coupled into a receive circuit like that used to measure a mutual capacitance at an intersection.
- the common mode noise may be coupled into the entire array 102 and may be sourced from system design elements, a user's finger, or some other global stimulus.
- FIG. 2 illustrates a half-bridge circuit 200 for measuring capacitance with suppressed common mode noise and imaging a fingerprint.
- Half-bridge circuit 200 may be disposed within FP controller 105 of FIG. 1 .
- half-bridge circuit 200 may be integrated into a host processor, the application processor of a computing device, or into a touch control circuit configured to detect the presence of conductive object on a touchscreen.
- a mutual capacitance, C MX between a row and column electrode (i.e. row electrode 104 and column electrode 106 of FIG. 1 ) is formed between a transmit (TX) node 211 and a receive (RX) node 213 .
- TX node 211 may be driven with a signal, TX, derived from a master signal, F TX , through buffer U 1 .
- Buffer U 1 may be configured to receive master signal F TX and to provide a TX signal, TX, by switching the signal line between a source voltage, V TX , and a ground potential. In other embodiments, different drive voltages and sink voltages for buffer U 1 may be used.
- a signal derived on TX signal TX and mutual capacitance C MX may be induced (or received) in RX node 213 and coupled to the positive input of low noise amplifier (LNA) 240 .
- LNA low noise amplifier
- a buried capacitance, C Dbb may be formed by the capacitance of a buried receive (RX) electrode to a buried drive electrode.
- a buried capacitance may be a capacitance that may not be changed or altered by the placement of a conductive object, such as a finger, near the array (see array 102 of FIG. 1 ).
- C Dbb may be driven in a similar manner to C MX , but with a complimentary TX signal, TX′, on TX′ node 212 .
- a signal based on complimentary signal TX′ and mutual capacitance C DBB may be received in RX node 213 and coupled to the positive input of low noise amplifier (LNA) 240 .
- LNA low noise amplifier
- Complimentary signal TX′ may be 180 degrees out of phase with signal TX.
- the physics of buried capacitance C Dbb may be similar to that of C MX . That is, C Dbb may be a mutual capacitance formed between a buried RX electrode and a buried TX electrode.
- the drive signal for C Dbb complimentary signal TX′, may be derived from F TX through buffer U 2 , just as was drive signal TX through buffer U 1 .
- buffer U 2 may invert F TX , also switching the signal line between source voltage V TX and a ground potential. This scheme may provide a signal that is complimentary to TX.
- different drive voltages and sink voltages may be used with buffer U 2 .
- RX node 213 shared between C MX and C Dbb may be coupled to a compensation circuit 230 .
- Compensation circuit 230 may be used to provide offset signals (like an induced current from a compensation signal TX COMP and a compensation capacitor, C COMP ) to better match C MX and C DBB across half-bridge circuit 200 .
- Compensation circuit 230 may include a modulator 232 with inputs from master signal F TX and a polarity signal “0/1” and an output to a buffer, U 3 .
- modulator 232 may be an XOR logic element. Using an XOR logic element as the modulator may provide a half-bridge circuit (such as half-bridge circuit 200 ) that is insensitive to variations in V TX .
- the TX COMP signal When polarity signal is logic 0, the TX COMP signal may be additive through C COMP to the signal on RX node 213 from TX node 211 .
- the TX COMP signal When the polarity signal is logic 1, the TX COMP signal may be additive through C COMP to the signal on RX node 213 from TX′ node 211 .
- Buffer U 3 may be configured to drive a compensation capacitor, C COMP , with a compensation signal, TX COMP .
- Compensation signal TX COMP may be generated by buffer U 3 by using the output of modulator 232 to alternate the input of buffer U 3 between a compensation voltage, V COMP , and a ground potential.
- the alternating output of buffer U 3 may be the compensation voltage, V COMP , or a ground potential (or a fixed potential of either polarity).
- V COMP may be provided by a regulated voltage divider, R DAC , between a supply voltage and a ground potential.
- V COMP may be provided by external supply voltages, fixed supply voltages within a chip containing the half-bridge circuit, or through a digital-to-analog converter (DAC).
- the supply voltage of regulated voltage divider R DAC may be V TX , the same voltage by which the drive signal outputs of buffers U 1 and U 2 is provided.
- Regulated voltage divider R DAC may be set with a look-up-table (LUT) for each intersection to be measured (each mutual capacitance C MX for the intersections between row electrodes 104 and column electrodes 106 of FIG.
- LUT look-up-table
- the supply voltages may be different than V TX and the ground potential may be another sink voltage.
- the output of regulated voltage divider R DAC may pass through a voltage follower, amplifier (Amp) 236 , to provide the drive potential, V COMP , to buffer U 3 .
- Half-bridge circuit 200 may include a low noise amplifier (LNA) 240 with a positive input coupled to RX node 213 .
- LNA low noise amplifier
- the bridge output is zero.
- LNA 240 may have a negative input coupled to a listener electrode 250 .
- the impedance of the listener electrode 250 equals the impedance of the RX electrode that is coupled to the positive input of LNA 240 .
- a noise signal that is injected to the sensor by the presence of a conductive object (e.g., a finger) is present on both inputs of LNA 240 .
- the noise is therefore common mode and may be suppressed by the differential input stage of LNA 240 through listener electrode 250 .
- Variations in manufacturing tolerances and the decrease in the mutual capacitance when a conductive object (e.g., a finger) is placed on the sensing surface may make it too difficult to match mutual capacitance C MX and buried capacitance C Dbb .
- the reduction in the mutual capacitance of C MX due to the placement of a conductive object (e.g., a finger) on the sensing surface may not be repeatable. Changes in the placement of the conductive object or of the specific properties of the conductive object may change the value of C MX differently on successive placements of the conductive object on the sensing surface.
- Compensation for variations in mutual capacitance C MX and buried capacitance C Dbb may be compensated for with compensation circuit 230 .
- Modulator 232 of compensation circuit may be formed with an XOR element with inputs from F TX and a “1/0” signal, as discussed above (see FIG. 2 ).
- compensation capacitance C COMP of compensation circuit 230 may be configured to provide enough signal to overcome the maximum imbalance between mutual capacitance C MX and buried capacitance C Dbb .
- compensation capacitance C COMP may be larger than the total possible error (tolerance) of mutual capacitance C MX and buried capacitance C Dbb .
- C COMP may be large enough to provide compensation for any mismatch in C MX and C Dbb .
- Configuring compensation capacitance C COMP to cover the maximum difference between or the total possible error of mutual capacitance C MX and buried capacitance C Dbb allows compensation circuit 230 to provide compensation for operation of half-bridge circuit 200 regardless of operational conditions. This compensation may provide for a more finely balanced (“tuned”) input to LNA 240 and a capacitance measurement for a change on mutual capacitance C MX (when a fingerprint ridge is present on the intersection of the selected row electrode 104 and column electrode 106 of FIG. 1 ).
- FIG. 2 illustrates a half-bridge circuit 200 that is configured for a single transmit signal, meaning that only one mutual capacitance (i.e., C MX ) is driven at a time.
- C MX mutual capacitance
- FIG. 3 illustrates a half-bridge circuit 300 configured to drive multiple TX electrodes simultaneously. Such operation may be referred to as “multi-TX” operation.
- Half-bridge circuit 300 may use similar blocks as half-bridge circuit 200 of FIG. 2 . However, an additional buffer, U 4 , may provide drive signal TX′′ at TX′′ node 314 to a second buried capacitance C Dbb2 coupled between buffer U 4 and RX node 213 .
- Drive signal TX′′ may be complimentary to signal TX, and therefore 180 degrees out of phase.
- Half-bridge circuit 300 may include a DBB control circuit, 310 , for buffers U 2 and U 4 .
- DBB control circuit 310 may provide signal F TX to the inputs D 1 and D 2 of buffers U 2 and U 4 , respectively, according to control inputs 311 and 312 , collectively, control inputs 313 .
- Control inputs 313 may be used to tune the output of buffers U 2 and U 4 to provide varying values of total capacitance through the multiple DBB capacitances, C DBB and C DBB2 .
- buried capacitance C Dbb2 may be three times as large as buried capacitance C Dbb .
- C MX _ A -C MX _ C may be driven with multiple phases of a TX signal
- the value of the sum of those multiple capacitances (C MX _ A -C MX _ C ) must be balanced on the other side of half-bridge circuit 300 . It is the combination of C Dbb and C Dbb2 that may provide that balancing and matching for the input of LNA 240 .
- Phase manipulation of the drive signals TX′ and TX′′ on buried capacitances C Dbb and C Dbb2 may provide more precise matching to the sum capacitance C MX _ SUM of the multiple driven TX electrodes 106 .
- the mutual capacitance of half-bridge circuit 300 may be the sum of however many mutual capacitances are active in multi-TX operation. For example, if four drive electrodes (i.e., column electrodes 106 in FIG. 4 ) are driven and one receive electrode (i.e., row electrodes 104 in FIG. 1 ) is coupled to LNA 240 , a total of four mutual capacitances may be coupled to the input of LNA 240 . It may be necessary, therefore to match the sum of those four mutual capacitances through the combination of C Dbb capacitances.
- C Dbb capacitances While only a pair of C Dbb capacitances are illustrated in FIG. 3 , more C Dbb capacitances may be implemented with more buffers and corresponding mutual capacitances between those buffers and the RX node 213 . Greater numbers of C Dbb capacitances may provide the ability to match the half-bridge capacitances of greater numbers of mutual capacitances, or with finer resolution, over and above the additional compensation resolution provided by compensation circuit 230 .
- FIG. 4 illustrates a system 400 including the half-bridge circuit 300 of FIG. 3 .
- An array of electrodes 402 may include row electrodes 404 and column electrodes 406 .
- Column electrodes 406 may be coupled to at least one TX buffer 408 (i.e., buffer U 1 of FIGS. 2 and 3 ), which may be coupled to a TX pattern generator 412 .
- TX pattern generator 412 may provide one or more TX patterns for the one or more column electrodes based on F TX (see FIGS. 2 and 3 ). While only eight electrodes are illustrated for each axis, one of ordinary skill in the art would understand that many more electrodes may be disposed in array 402 to provide sufficient size and resolution to a measurement circuit. As explained with above with regard to FIG.
- Electrodes may be disposed on each axis to provide the necessary resolution.
- the pitch of the electrodes may be such that multiple electrodes are disposed for every ridge or valley of a fingerprint.
- electrodes may be disposed such that multiple electrodes may be affected by the presence of a conductive object, such as a finger, on the array.
- Row electrodes 404 of array 402 may form a mutual capacitance with column electrodes 406 (see C MX of FIGS. 1 and 2 and C MX _ A ⁇ C MX _ C of FIG. 3 ).
- Row electrodes 404 may be coupled to a positive input of a low noise amplifier (LNA) 440 through an RX multiplexor 430 coupled to RX node 213 .
- LNA low noise amplifier
- RX multiplexor 430 may be configured to couple a single row electrode to the positive input of LNA 440 at a time.
- multiple row electrodes may be coupled to the positive input of LNA 440 simultaneously.
- multiple LNAs may be coupled to RX multiplexor 430 to allow for individual and simultaneous measurement.
- RX multiplexor 430 may be comprised of several smaller multiplexors, either in parallel or in series, with various input and output configurations.
- System 400 may also include a listener electrode 410 in close physical proximity to array 402 .
- Listener electrode 410 may be coupled to the negative input of LNA 440 as described above with regard to FIGS. 2 and 3 (see listener electrode 250 and LNA 240 ).
- a first buried electrode 251 may be coupled to the positive input of LNA 440 at RX node 213 .
- a second buried electrode 253 and a third buried electrode 255 may be disposed in such a manner that a mutual capacitance (C DBB _ 3 and C DBB _ 5 ) is formed between each and the first buried electrode 251 .
- the size of the buried capacitances for C Dbb and C Dbb2 may be defined by the size of the buried electrodes and the space between them. Capacitance is given by:
- Buried electrodes 253 and 255 may be coupled to outputs of buffers U 2 and U 4 , respectively (as illustrated in FIG. 3 ). Control of buffers U 2 and U 4 may be achieved with a DBB Control circuit 260 , which is also described in detail with regard to FIG. 3 above.
- the drive scheme for providing the varied buried capacitance values to the positive input of LNA for matching with the mutual capacitance between row electrodes 404 and column electrodes 406 (C MX of FIGS. 2 and 3 ) is shown in Table 1, as an example.
- a compensation electrode 257 may be disposed such that a mutual capacitance is formed between compensation electrode 257 and first buried electrode 251 .
- the output of buffer U 3 (also illustrated in FIGS. 2 and 3 ) may be coupled to compensation electrode 257 .
- Buffer U 3 may be controlled my modulator 432 as illustrated in FIGS. 2 and 3 and provide a signal that is switched between ground and a compensation voltage, V COMP , set by a digital-to-analog converter 434 (R DAC and amplifier A of FIGS. 2 and 3 ).
- the output of LNA 440 may be coupled to a demodulation circuit (“demodulator”) 450 , which provides an analog to analog-to-digital converter (ADC) 452 .
- demodulation circuit 450 and ADC 452 may be similar to that described in U.S. patent application Ser. No. 14/672,036, which is herein incorporated by reference.
- Master signal F TX which may be used to provide the various drive frequencies to the capacitances of the half-bridge of system 400 may be provided by digital subsystem 470 .
- Digital subsystem 470 may include a clock generator 471 , which may provide a base clock frequency for drive and control functions.
- Digital subsystem 470 may also include CPU 473 which may be configured to execute functions and programs stored in memory 475 and to control registers (“Reg”) 477 for circuit operation and interconnect control.
- digital subsystem 470 may include digital I/O 479 configurable for communication with a host controller or an AFE control circuit (not shown).
- FIG. 5 illustrates one embodiment of a fingerprint sensor 500 including the electrodes similar to those illustrated in FIG. 4 (rows 404 and column 406 of array 402 .
- Fingerprint sensor 500 may include an array of electrodes 502 which form the mutual capacitances (i.e., C MX of FIGS. 1 and 2 and C MX _ A -C MX _ C of FIG. 3 ).
- Array 502 may include a plurality of row electrodes 504 and a plurality of column electrodes 506 . While only eight electrodes are illustrated for each axis, this is merely for ease of description.
- a fingerprint measurement array may include dozens or hundreds of electrodes disposed as rows and columns.
- Row electrodes 504 and column electrodes 506 may be coupled to receive (RX) and drive (TX) circuitry, respectively, as shown and described in FIG. 4 . Electrodes (columns and rows) with dashed lines indicate that considerably more columns or rows may be disposed along either axis. While only eight electrodes (rows 504 and columns 506 ) are illustrated, this is merely for simplicity of description. One of ordinary skill in the art would understand that columns and rows that are dashed represent dozens or even hundreds of electrodes.
- a listener electrode 510 may be disposed in close proximity to array 502 and coupled to an input of an LNA (as illustrated in FIGS. 2 and 3 ). Listener electrode may be disposed such that contact with array 502 necessarily provides contact with listener electrode 510 . Listener electrode 510 may be used to provide common mode noise rejection through differential inputs to an LNA.
- FIG. 6A illustrates one embodiment of a fingerprint sensor 600 including column electrodes similar to those illustrated in FIGS. 4 and 5 (see column electrodes 406 and 506 ).
- column electrodes 606 may be coupled to the positive input of LNA 440 and the row electrodes (not shown for clarity of description) may be coupled to a plurality of TX buffers ( 412 of FIG. 4 ).
- Fingerprint sensor 600 may also include a listener electrode 610 disposed along an edge of fingerprint sensor 600 .
- listener electrode 610 may be constructed and disposed in such a way that any touch that may generate information sufficient for a fingerprint image (and subsequent decisions) necessarily contact listener electrode 610 .
- the common mode noise rejection provided by the listener electrode 610 through the differential input i.e. LNA 240 of FIGS. 2 and 3 .
- Differential input may be ensured since a finger will always be in contact with the listener electrode when fingerprint sensor 600 is active and capable of imaging a fingerprint.
- FIG. 6B illustrates another embodiment of a fingerprint sensor 601 including column electrodes 606 similar to those illustrated in FIGS. 4, 5, and 6A .
- column electrodes 606 may be coupled to the positive input of LNA 440 (see FIG. 4 ) and the row electrodes (not shown for clarity of description) may be coupled to a plurality of TX buffers ( 412 of FIG. 4 ).
- Fingerprint sensor 601 may also include a listener electrode 611 disposed at an edge and near the center of fingerprint sensor 601 .
- listener electrode 611 may be constructed and disposed in such a way that any touch than may generate information sufficient for a fingerprint image (and subsequent biometric decisions) will contact listener electrode 610 .
- the common mode noise rejection provided by the listener electrode 610 is ensured since a finger will always be in contact with the listener electrode when fingerprint sensor 600 is active and capable of imaging a fingerprint.
- FIG. 7A illustrates one embodiment of a fingerprint sensor 700 with an array of electrodes 702 .
- Array 702 may include a plurality of column electrodes 706 and a plurality of row electrodes 704 .
- Row electrodes 704 may be coupled to drive circuitry as described in FIGS. 2-4 .
- Column electrodes may be coupled to a LNA (similar to LNA 240 and 440 of FIGS. 2-4 ).
- Fingerprint sensor 700 may include at least one split electrode 705 (comprising split electrode halves 705 . 1 and 705 . 2 ) amongst the column electrodes 706 that may be coupled to the LNA ( 440 of FIG. 4 ).
- a split electrode 705 may be one that has a break 715 at some point between one side of the array and the other. While FIG. 7A shows that the break 715 is in the center of split electrode 705 , break 715 may be positioned elsewhere along the axis of the split electrode 705 . Break 715 may provide galvanic isolation to split electrode halves 705 . 1 and 705 . 2 . Electrodes (columns and rows) with dashed lines indicate that considerably more columns or rows may be disposed along either axis. While only eight electrodes (rows 704 and columns 706 ) are illustrated, this is merely for simplicity of description. One of ordinary skill in the art would understand that columns and rows that are dashed represent dozens or even hundreds of electrodes.
- Fingerprint sensor 700 may provide listener electrode functionality similar to that illustrated in FIGS. 6A and 6B , but with in-grid electrodes. This configuration may provide a greater probability of contact between a finger and the listener electrode when split electrode 705 is configured as such.
- a row electrode coupled to a drive circuit thus making it a drive electrode (TX electrode) under split electrode 705 . 1 is energized
- TX electrode drive electrode
- the mutual capacitances between column electrodes 706 and the energized row electrode are measured.
- the mutual capacitance (as illustrated in FIG. 1 ) between split electrode 705 . 1 and the energized row electrode is measured as is the mutual capacitance of the rest of the column electrodes is measured.
- the listener electrode which is coupled to the negative input of a LNA (as shown in FIGS. 2-4 ).
- the upper portion of split electrode 705 ( 705 . 1 ) may be used as the listener electrode.
- the upper and lower portions of split electrode 705 halves 705 . 1 and 705 . 2 , respectively
- the adjacent portions of split electrode 705 may be coupled together in parallel to provide similar area to standard column electrodes.
- the noise coupling from a finger may then be balanced and provide the common noise rejection of the listener electrode (e.g. 250 of FIGS. 2 and 3, 410 of FIG. 4 ) with the differential input stage of LNA (e.g. 240 of FIGS. 2 and 3 and 440 of FIG. 4 ).
- Balanced capacitances may have similar capacitance values on either side of RX node 213 (of FIGS. 2 and 3 ).
- FIG. 7B illustrates one embodiment of a fingerprint sensor 701 with an array of electrodes 722 .
- Array 722 may include a plurality of column electrodes 726 and a plurality of row electrodes 723 and 724 .
- Row electrodes 723 and 724 may be coupled to drive circuitry as described in FIGS. 2-4 .
- Column electrodes may be coupled to an LNA (similar to LNA 240 and 440 of FIGS. 2-4 ).
- Row electrodes 723 and 724 may each extend only partially across array 722 , but the combination thereof my provide complete coverage of array 722 .
- the mutual capacitances between column electrodes 726 and row electrodes 723 may be measured while the column electrodes 726 that intersect row electrodes 724 may be used similar to listener electrode 250 of FIGS. 2 and 3 and listener electrode 410 of FIG. 4 .
- the mutual capacitances between column electrodes 726 and row electrodes 724 may be measured, while the column electrodes 726 that intersect row electrodes 723 are used similar to listener electrode 250 of FIGS. 2 and 3 and listener electrode 410 of FIG. 4 .
- twice as many drive pins of a drive circuit may be required to drive both sides of the row electrodes 723 and 724 .
- column electrodes need not be coupled in parallel since they can be used in their entirety.
- Figures and associated descriptions are directed to a device resembling a mobile handset with a touchscreen.
- one of ordinary skill in the art may apply the techniques described to larger touch-enabled consumer devices, such as tablets and personal computers. Additionally, the techniques described may be applied to smaller touch-enabled consumer devices, such as watches, GPS unit, media players, etc.
- consumer electronics are referenced above, secure entry for various functions may be used in home automation applications (home entry, appliances, HVAC control, lighting, and media control) as well as automotive applications.
- example or “exemplary” are used herein to mean serving as an example, instance or illustration. Any aspect or design described herein as “example” or “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, use of the words “example” or “exemplary” is intended to present concepts in a concrete fashion.
- the term “or” is intended to mean an inclusive “or” rather than an exclusive “or.” That is, unless specified otherwise, or clear from context, “X includes A or B” is intended to mean any of the natural inclusive permutations. That is, if X includes A; X includes B; or X includes both A and B, then “X includes A or B” is satisfied under any of the foregoing instances.
- Embodiments described herein may also relate to an apparatus for performing the operations herein.
- This apparatus may be specially constructed for the required purposes, or it may comprise a general-purpose computer selectively activated or reconfigured by a computer program stored in the computer.
- a computer program may be stored in a non-transitory computer-readable storage medium, such as, but not limited to, any type of disk including floppy disks, optical disks, CD-ROMs and magnetic-optical disks, read-only memories (ROMs), random access memories (RAMs), EPROMs, EEPROMs, magnetic or optical cards, flash memory, or any type of media suitable for storing electronic instructions.
- computer-readable storage medium should be taken to include a single medium or multiple media (e.g., a centralized or distributed database and/or associated caches and servers) that store one or more sets of instructions.
- the term “computer-readable medium” shall also be taken to include any medium that is capable of storing, encoding or carrying a set of instructions for execution by the machine and that causes the machine to perform any one or more of the methodologies of the present embodiments.
- the term “computer-readable storage medium” shall accordingly be taken to include, but not be limited to, solid-state memories, optical media, magnetic media, any medium that is capable of storing a set of instructions for execution by the machine and that causes the machine to perform any one or more of the methodologies of the present embodiments.
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Abstract
Description
TABLE 1 | ||||
Control Signal | 00 | 01 | 10 | 11 |
D1 Input | FTX | /FTX | Z | FTX |
D2 Input | Z | FTX | FTX | FTX |
Total DBB | 1 × CDbb | 2 × CDbb | 3 × CDbb | 4 × CDbb |
Capacitance | ||||
Total DBB Capacitance=C DBB2 −C DBB=2*C DBB.
where C is capacitance in Farads, A is the area of overlap between the row and column electrodes of the buried capacitances, εr is the relative static permittivity (dielectric constant) of the material between the row and column electrodes (plates of a capacitor), ε0 is the electric constant, and d is the separation between the row and column electrodes (plates of the capacitor).
Claims (12)
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US14/978,442 US10380397B2 (en) | 2015-09-09 | 2015-12-22 | Half-bridge fingeprint sensing method |
CN201680048165.3A CN107924460B (en) | 2015-09-09 | 2016-09-02 | Half-bridge fingerprint sensing method |
PCT/US2016/050186 WO2017044386A1 (en) | 2015-09-09 | 2016-09-02 | Half-bridge fingerprint sensing method |
DE112016004090.3T DE112016004090T5 (en) | 2015-09-09 | 2016-09-02 | HALF BRIDGE FINGERPRINT DETECTION METHOD |
US16/507,344 US20200005011A1 (en) | 2015-09-09 | 2019-07-10 | Half-bridge Fingeprint Sensing Method |
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
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US201562216241P | 2015-09-09 | 2015-09-09 | |
US201562216253P | 2015-09-09 | 2015-09-09 | |
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EP3724814A4 (en) * | 2017-12-11 | 2021-02-24 | Fingerprint Cards AB | Fingerprint sensing arrangement |
CN108805066B (en) * | 2018-05-31 | 2020-04-17 | 京东方科技集团股份有限公司 | Fingerprint detection device and fingerprint detection method |
CN111796723B (en) * | 2019-10-11 | 2023-06-02 | 武汉华星光电半导体显示技术有限公司 | Touch sensing device and touch display panel |
CN110874586B (en) * | 2019-11-29 | 2023-06-30 | 厦门天马微电子有限公司 | Display panel and display device |
US11222933B2 (en) * | 2020-04-28 | 2022-01-11 | Himax Technologies Limited | Display panel equipped with function of detecting an object, and method for detecting an object on a display panel |
Citations (20)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6108438A (en) * | 1997-04-29 | 2000-08-22 | U.S. Philips Corporation | Fingerprint sensing devices and systems incorporating such |
US20030035570A1 (en) * | 2000-12-05 | 2003-02-20 | Validity, Inc. | Swiped aperture capacitive fingerprint sensing systems and methods |
US20030035572A1 (en) * | 1997-09-11 | 2003-02-20 | Stmicroelectronics Inc. | Electrostatic discharge protection of a capacitive type fingerprint sensing array |
US7460697B2 (en) | 2005-07-19 | 2008-12-02 | Validity Sensors, Inc. | Electronic fingerprint sensor with differential noise cancellation |
US7735721B1 (en) | 1999-11-30 | 2010-06-15 | Diebold Self-Service Systems Division Of Diebold, Incorporated | Method of evaluating checks deposited into a cash dispensing automated banking machine |
US8115497B2 (en) * | 2007-11-13 | 2012-02-14 | Authentec, Inc. | Pixel sensing circuit with common mode cancellation |
US20130009651A1 (en) * | 2010-01-15 | 2013-01-10 | Picofield Technologies Inc. | Biometric Image Sensing |
US20130221993A1 (en) | 2012-02-24 | 2013-08-29 | Petro Ksondzyk | Frequency hopping algorithm for capacitance sensing devices |
US20130265242A1 (en) * | 2012-04-09 | 2013-10-10 | Peter W. Richards | Touch sensor common mode noise recovery |
WO2014021918A1 (en) | 2012-07-31 | 2014-02-06 | Cypress Semiconductor Corporation | Usage of weighting matrices in multi-phase scanning modes |
US20140085252A1 (en) * | 2012-09-26 | 2014-03-27 | Ingar Hanssen | Increasing the dynamic range of an integrator based mutual-capacitance measurement circuit |
US8736577B2 (en) | 2007-01-03 | 2014-05-27 | Apple Inc. | Storing baseline information in EEPROM |
US8786295B2 (en) | 2011-04-20 | 2014-07-22 | Cypress Semiconductor Corporation | Current sensing apparatus and method for a capacitance-sensing device |
US8874396B1 (en) | 2013-06-28 | 2014-10-28 | Cypress Semiconductor Corporation | Injected touch noise analysis |
US20150022670A1 (en) | 2013-07-22 | 2015-01-22 | Apple Inc. | Noise Compensation in a Biometric Sensing Device |
US8952916B2 (en) | 2005-11-15 | 2015-02-10 | Synaptics Incorporated | Methods and systems for detecting a position-based attribute of an object using digital codes |
US9013441B2 (en) | 2010-08-24 | 2015-04-21 | Cypress Semiconductor Corporation | Smart scanning for a capacitive sensing array |
US9019220B1 (en) | 2012-03-14 | 2015-04-28 | Cypress Semiconductor Corporation | Baseline charge compensation |
US20150268783A1 (en) | 2014-03-24 | 2015-09-24 | Hideep Inc. | Touch detection method and touch detector performing the same |
US20160342265A1 (en) * | 2014-01-03 | 2016-11-24 | 3M Innovative Properties Company | Capacitive touch systems and methods using differential signal techniques |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US8093914B2 (en) * | 2007-12-14 | 2012-01-10 | Cypress Semiconductor Corporation | Compensation circuit for a TX-RX capacitive sensor |
US9104922B2 (en) * | 2012-06-15 | 2015-08-11 | Honeywell International Inc. | Anisotropic magneto-resistance (AMR) gradiometer/magnetometer to read a magnetic track |
KR102207193B1 (en) * | 2013-12-31 | 2021-01-26 | 엘지디스플레이 주식회사 | Touch sensing system |
EP2937767A1 (en) * | 2014-03-27 | 2015-10-28 | LG Display Co., Ltd. | Touch panel, display device and method of driving the same |
CN104376299B (en) * | 2014-10-16 | 2017-09-01 | 北京集创北方科技股份有限公司 | A kind of fingerprint Identification sensor |
-
2015
- 2015-12-22 US US14/978,442 patent/US10380397B2/en active Active
-
2016
- 2016-09-02 DE DE112016004090.3T patent/DE112016004090T5/en active Pending
- 2016-09-02 WO PCT/US2016/050186 patent/WO2017044386A1/en active Application Filing
- 2016-09-02 CN CN201680048165.3A patent/CN107924460B/en active Active
-
2019
- 2019-07-10 US US16/507,344 patent/US20200005011A1/en active Pending
Patent Citations (20)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6108438A (en) * | 1997-04-29 | 2000-08-22 | U.S. Philips Corporation | Fingerprint sensing devices and systems incorporating such |
US20030035572A1 (en) * | 1997-09-11 | 2003-02-20 | Stmicroelectronics Inc. | Electrostatic discharge protection of a capacitive type fingerprint sensing array |
US7735721B1 (en) | 1999-11-30 | 2010-06-15 | Diebold Self-Service Systems Division Of Diebold, Incorporated | Method of evaluating checks deposited into a cash dispensing automated banking machine |
US20030035570A1 (en) * | 2000-12-05 | 2003-02-20 | Validity, Inc. | Swiped aperture capacitive fingerprint sensing systems and methods |
US7460697B2 (en) | 2005-07-19 | 2008-12-02 | Validity Sensors, Inc. | Electronic fingerprint sensor with differential noise cancellation |
US8952916B2 (en) | 2005-11-15 | 2015-02-10 | Synaptics Incorporated | Methods and systems for detecting a position-based attribute of an object using digital codes |
US8736577B2 (en) | 2007-01-03 | 2014-05-27 | Apple Inc. | Storing baseline information in EEPROM |
US8115497B2 (en) * | 2007-11-13 | 2012-02-14 | Authentec, Inc. | Pixel sensing circuit with common mode cancellation |
US20130009651A1 (en) * | 2010-01-15 | 2013-01-10 | Picofield Technologies Inc. | Biometric Image Sensing |
US9013441B2 (en) | 2010-08-24 | 2015-04-21 | Cypress Semiconductor Corporation | Smart scanning for a capacitive sensing array |
US8786295B2 (en) | 2011-04-20 | 2014-07-22 | Cypress Semiconductor Corporation | Current sensing apparatus and method for a capacitance-sensing device |
US20130221993A1 (en) | 2012-02-24 | 2013-08-29 | Petro Ksondzyk | Frequency hopping algorithm for capacitance sensing devices |
US9019220B1 (en) | 2012-03-14 | 2015-04-28 | Cypress Semiconductor Corporation | Baseline charge compensation |
US20130265242A1 (en) * | 2012-04-09 | 2013-10-10 | Peter W. Richards | Touch sensor common mode noise recovery |
WO2014021918A1 (en) | 2012-07-31 | 2014-02-06 | Cypress Semiconductor Corporation | Usage of weighting matrices in multi-phase scanning modes |
US20140085252A1 (en) * | 2012-09-26 | 2014-03-27 | Ingar Hanssen | Increasing the dynamic range of an integrator based mutual-capacitance measurement circuit |
US8874396B1 (en) | 2013-06-28 | 2014-10-28 | Cypress Semiconductor Corporation | Injected touch noise analysis |
US20150022670A1 (en) | 2013-07-22 | 2015-01-22 | Apple Inc. | Noise Compensation in a Biometric Sensing Device |
US20160342265A1 (en) * | 2014-01-03 | 2016-11-24 | 3M Innovative Properties Company | Capacitive touch systems and methods using differential signal techniques |
US20150268783A1 (en) | 2014-03-24 | 2015-09-24 | Hideep Inc. | Touch detection method and touch detector performing the same |
Non-Patent Citations (10)
Title |
---|
Davison, Burk, "Techniques for Robust Touch Sensing Design," dated Nov. 29, 2012, 30 pages. |
International Search Report for International Application No. PCT/US2016/050186 dated Sep. 27, 2016; 4 pages. |
Mohamed Gamal, et al., "Concurrent Driving Method with Fast Scan Rate for Large Mutual Capacitance Touch Screens," Journal of Sensors, Apr. 2014, 7 pages. |
Shruti H, et al. "Designing a Capacitive Sensing System for a Specific Application," Dec. 2011, 14 pages, Cypress Semiconductor Corporation, EE Times. |
Srinivasagam, Kannan, et al., "Differentiating Noise from Real Touch-The Key to Robust Capacitive Sensing," Oct. 2010, 8 pages, Cypress Semiconductor Corporation, EE Times Design. |
Srinivasagam, Kannan, et al., "Differentiating Noise from Real Touch—The Key to Robust Capacitive Sensing," Oct. 2010, 8 pages, Cypress Semiconductor Corporation, EE Times Design. |
USPTO Advisory Action for U.S. Appl. No. 14/964,562 dated Apr. 10, 2017; 4 pages. |
USPTO Applicant Initiated Interview Summary for U.S. Appl. No. 14/964,562 dated Apr. 5, 2017; 3 pages. |
USPTO Non Final Rejection for Application No. 16/017,513 dated Jun. 25, 2019; 17 pages. |
Written Opinion of the International Searching Authority for International Application No. PCT/US2016/05186 dated Sep. 27, 2016; 6 pages. |
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